Thermostatic control



June 27, 1939 R, E LL 2,163,801

THERMOSTATIC CONTROL Original Filed Dec. '7, 1935 I312 (sssv z DIME? a v m 4 if, j 5. H

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Patented June. 27, 1939 UNlTED STATES 2,163,801 THERMOSTATIC coN'rnoL Robert E. Newell, Youngwood, Pa., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania Application Claims.

This'invention relates to thermostatic controls in which a single control member is arranged to be operated in accordance with the demands of two thermostats a is particularly useful for 5 controls in whigh/fia two thermostats are, located in different he zones with the control member being operated in accordance with temperature variations in one heat zone and independently operated upon the development of an abnormal temperature condition in the other heat zone.

For illustrative purposes the invention is shown as adapted for use with a gas heating burner, and a pilot burner, although it may obviously be adapted for other uses. In this preferred adaptation, I provide a single valve operable in accordance with the presence or absence of a pilot flame and also operable, during the presence of the pilot flame, in response to the temperature of the medium to be controlled. The

valve is so arranged that it will not be opened unless two conditions are fulfilled; first, the pilots must be burning, and second, the temperature of the medium must be lower than that desired. However, the valve will be shut ofi if either the pilot flame is extinguished or the medium reaches the desired temperature. In other words, as long as the pilot is burning, the valve will be freely and independently regulated by a first thermostat respon'sive to the temperature of the medium; but if the pilot is not burning, the valve will be moved to a closed position, regardless of the temperature of the mediunnby a second thermostat which is located within'the heat zone of the pilot burner.

It has been customary heretofore in installing thermostatic controls to use two automatically operated valves, one for temperature control and one for a safety pilot control. As the fuel passes through each valve, an undesirable drop in fuel pressure occurs. It is quite apparent thatv 40 the provision of one valve to take the place of two is advantageous not only in reducing the pressure drop in the fuel supply line, but also in reducing the cost of the control. Installation of the control is thus simplified as it is only necessary to insert one automatic yalve instead of two. Thus the cost of one valve structure and the expense of the installation thereof is eliminated. The fact that the valve which is to be used as asafety control is in constant operation under the influence of the temperature-control thermostat is also a distin t advantage of my invention. The

usual safety ilot control heretofore employed consisted of n independent valve which was opened when the pilot was first ignited at the istime 'of installation, and was-designed to auto- December I, 1935, Serial No. 53,359

Renewed May 8, 1939 matically close if the pilot flame was extinguished. However, every effort was put forth to provide a piloifburner whose flame would not go out and consequently the safety valve would often remain open for a rather lengthy period, after which the valve may have taken a set position and because of dirt, hardened grease, loss of spring tension or other reasons,would not close properly if the pilot flame went out. Such a condition rendered the safety control undependable. As previously mentioned, the valve of my" device is constantly operated and kept in working condition by the temperature control-thermostat and any defect would be immediately noticeable.

In the illustrated embodiment of my invention, I provide a thermostatically actuated snap acting mechanism operatively connected with the valve. Means other than a snap acting mechanism may be employed but it is believed to be more difficult to accomplish the desired result with a snap acting mechanism, and the value of a snap acting valve is well known to those acquainted with the thermostatic art. This mechanism is so constructed as to constantly tend, of itself, to open the valve, and the two thermostats engage the mechanism to oppose its normal tendency and allow the valve to be closed. By having the mechanism tending, of itself, to open the valve, it is possible to arrange. the two thermostatsso that the forces developed thereby will never oppose each other.

It is often desirable in thermal control systems to include an auxiliary control to regulate the operation of a fan, an air shutter, or some other device such as is commonly used to increase the eiflciency of the system.' For this purpose, I have provided an auxiliary control member which is actuated by the primary control orvalve operat ing means. This auxiliary control member may in turn operate a switch, valve or other suitable means for regulating the operation of the particular device tobe. used. e In the structure shown, I have used for the temperature control, a bellows type thermostat having a capillary tube connecting the bellows with a sensitive bulb which is placed in the medium to' be controlled, thus allowing considerable flexibility in installation. For the safety pilot thermostat, I have used a rod and tube thermostat of particular construction for rapid response 50 to extinguishment of the pilot flame and to simplify installation, a pilot burner has been rigidly mounted on the control casing 'which insures the pilot flame being located in the proper position relative to the safety pilot thermostat. Incor-, ll

within the same casing. Thus the preferred device assembles all the necessarily manually operable controls into one compact structure with the automatic controls, Such a structure is advantageous to the user both from the standpoint of expense and of convenience. Of course it is not absolutely necessary to used such a combination with the automatically controlled valve, but the ease of installation and convenience of operation make such a device desirable. In this drawing:

Figure 1 is a vertical sectional view through a structure embodying the present invention;

Figure 2 is a side elevation view of the device;

Figure 3 is a plan view of the snap acting mechanism actuating pin shown in Figure 1;

Figure 4 is a view showing the assembled relation of the parts of the snap acting mechanism for operating the valve;

Figure 5 is an elevation view ating lever of the mechanism;

Figure 6 is an elevation view of the main lever of the mechanism; and

Figure 7 is a plan view of the bridge or lever supporting member.

As illustrated in this drawing, l indicates the valve casing having an inlet 2 and an outlet 3 fromwhich the gas passes to a. heating burner which is not shown. Adjoining the inlet is a chamber l which is so shaped as to form a dirt trap to collect any foreign matter in the gas which might otherwise be carried into the valve proper. A gas cock 5 of the conventional tapered plug type is positioned within the casing l to control the flow of gas from the chamber 4 to the automatically operated valve 6. The plug cock 5 fits in a tapered bore 7 and has an axial passage 8, communicating with chamber 4 and having a port 9 arranged to cooperate with a second passage l0 leading through the casing to valve 6. A handle H is mounted on the cock outside of the casing to permit manual rotation of the plug 5 to move port 9 into or out ofv alignment with, the passage II]. A spring I2 is located between a cap l3, secured to the casing by screws l4, and a washer l5 mounted on the cock 5, and serves to hold the tapered plug in place.

The valve 6 cooperates with a valve seat l6 formed in the casing to control the flow of gas through the passage I0. Positioned on the casing adjacent valve 6 is a valve cap H- which may be removed to allow cleaning of the valve and seat. A spring l8 between the cap and the valve constantly urges the valve toward its seat. The valve is arranged to be operated by a lever or snap acting mechanism to be hereinafter described and has a guide pin l9 which slides back and forth in the bore 20 in the cap 11.

A large chamber 2| within the casing l is connected with passage ID by an opening in the upper end of the left wall of the chamber, said opening being' concentric with the valve seat 16 so that the stem 22 of the valve extends into the chamber 2|. Thus the gas flows through the inlet 2 to chamber 4, thence through cock 5, passage I0 and past valve s into chamber 2i and out the outlet 3 in the bottom of chamber 29.

Mounted substantially vertically in chamber 26 is the main lever 23 of the snap acting mechanism. Two small projections from lever 23 a short distance below the upper extremity thereof the valve operof, are equipped with knife edges 24 which 00- operate with v shaped grooves or bearings provided in portions 25 which extend downwardly from the upper wall of the chamber 2| on each side of the upper end of the lever 23. Thus, the main lever is pivoted intermediate the ends thereof which remain free to move.

A secondary or valve operating lever 26 is mounted in the chamber 2| substantially parallel to the main lever 23, with its upper end arranged to engage the stem 22 of the valve 6. The lower endof lever 26 is forked to receive a tension spring 21 whose upper end is hooked into the hole 28 in the lever 26 and whose lower end is hooked over the lower end of the main lever 23, thus interconnecting the two levers. The forked arms 29 of the lever 26 are also provided with knife edges 30 arranged to cooperate with bearings 3! carried by the arms 32 of a horseshoe shaped bridge member 33. The extremities of the arms 32 are also equipped with knife edges 34 which rest in bearings formed in the side wall of chamber 2|. The horseshoe shaped bridge extends substantially horizontally across the bottom of the chamber with the knife edges in the hearings on the left and the curved portion on the right being supported by an adjusting screw 35 which protrudes through a threaded opening 36 in the casing to engage a recess 31 in the bridge. Movement of the screw 35 up and down raises or lowers the end of the bridge and thus changes the relative positions of the bearings of the two levers and effects an adjustment of the tension of the spring 21.

As described, the snap acting mechanism thus consists of, a main lever pivoted on knife edges intermediate the ends thereof, a secondary lever pivoted at its lower end on a horseshoe shaped bridge, and a tension spring interconnecting the middle of the secondary lever and the lower end of the main lever which is free to move back and forth between the arms of the bridge. Both the main and secondary levers are thus held in their bearings by the tension spring. As the main lever is rotated clockwise about its pivot, the lower end of the tension spring is also rotated about'the point of its connection to the secondary lever. As soon as the line of force of this spring passes to the left of the plane of the point of connection 28 of the tension spring and the points of bearing 30 of the secondary lever, said lever will be snapped to the left about its bearings and the upper end of the lever will strike the valve stem and open the valve. Similarly, counter-clockwise movement of the main lever will cause the secondary lever to be snapped to the right and allow the valve to be closed.

It is necessary for the proper operation of this particular structure that the levers be so shaped that the point 28 at which the tension spring 2! is hooked to the secondary lever is always on the left of a line between the knife edged pivots 24 and 30. Then when the upper end of the secondary lever 26 is snapped to the right as a result of rotation of the main lever by one of the thermostats, the tension spring still tends to pull the lower end of lever 23 and the upper end of lever 26 together. The lever 26 cannot be moved any further to the right, the direction of the line offorce of the spring on that lever, but as soon as the forces of-both thermostats are re= moved from the lever 23, the spring 21, since the point 28 is to the left of line 2-30, will pull the lower end of 23 to the left about pivots 24 until the line-of force of the spring passes to left position to in turn hold .the valve 6 open,

and, in order to then snap lever 26 to the right and allow'the valve 4 to be shut, a force must be exerted on the main lever 23 to move its lower end to the right. When this force is removed 10' the lever 26 will be snapped to the left as above described.

One side of the casing I is left open to allow installation of the snap acting mechanism and is thereafter sealed by a gas-tight cover 68 held on by screws 69. An opening in the casing at the upper end of chamber 2| on the opposite side of the levers from the valve permits the extension therethrough of a substantially horizontal rod 38 which engages the upper end of the main my lever 23 above its pivot points. A. series of glands on the rod 38 prevent the leakage of gas around the rod which extends outwardly from the casing i for any desired distance. 'Ihe outer extremity of rod 38 abuts against one end of a smaller rod 25 39, the other end of which bears against the plugged end of a tube which encases the rod 39 and the portion of the rod 38 which extends without the casing l.- The tube." is screwed into casing l and held in place by nut 4|. The

so small rod 39 is made of a relatively non-expansible material and is held in a central position by guides 42, while both the tube 40 and tharod 4 through passage 44 in the casing i and pipe 45 which is mounted on the casing directly below the tube to. I having a handle 47 on the exterior of the casing, 45 is inserted in passage 42, whereby the gas to the pilot flame may be manually shut off or turned on, as the case may be. Another small but quite accurately'adjustable valve 48 is located at the entrance to pipe 45 and is arranged to permit regulation of the quantity of gas to be passed 'to the pilot flame. An oriflce 49 is mounted within the pipe 45 just ahead of an opening to therein to cause the gas to be mixed with the proper amount of air for combustion. The lengths of the tube 40 and rods 38 and 39 are so designed that when the pilot is not burning, the rod 38 will be far enough to the left to have rotated the main lever fl suiiiciently to have snapped lever 28 to the right and allowed valve expanded length of the tube and the combined lengths of the rods "and I0 wfll allow the main lever to be rotated clockwise and the secondary lever snapped to the left to open the valve, assuming that no other force is applied to the mechanism. It the pilot'flame is extinguished the rod and tube thermostat will cool and the valve "ll will again be closed.

A small plug type gas cock 46 than the opening in the cap. This shoulder rests The provision of the non-expansible rod 39 in the portion of the tube 4|, which is directly subjected to the flame of the pilot burner, and the rod 38 having substantially the same coeilicient to the portion containing the expansible rod,

whereupon both this portion and the rod will expand equally and the valve will not be affected. 15

Now, if the pilot flame is subsequently extinguished, the portion of the tube that had been subjected to the flame will cool quite rapidly and the other portion having a greater and more exposed surface will cool quicker than the expanded go;

rod within. Thus, the contraction of the tube will take place while the rod 38 is still in an expanded condition and the valve will be closed in a very short time after the pilot is extinguished.

If a single non-expansible rod were used in place 25- does not aflect the snap mechanism or the valve so:

as long as the pilot is burning, but which will cause the valve to be closed if the pilot is extinguished and will lock the snap mechanism to prevent reopening of the valve until the pilot is re-ignited.

Extending through an opening in the casing wall near the bottom of chamber 2! and substantially parallel to but on the opposite side of the levers from the rod II, is a gland pin 59. The (right end-of the pin Ii passes between the arms of the bridge 33 and abuts against the lower end of the main lever 23, the pin having a vertical slot 52 through whichpasses the end of the ten sion spring which also engages the lower end. of the main lever. The other extremity of pin 5i bears against a plate 53 which covers the free end of a flexible bellows 54, and also serves as a mounting for a load spring 55v situated'between the plate. and the casing I. The other end of the bellows 54 consists of a threaded projection 56 do. which cooperates with a threaded bore in an operating knob 51. A tubular sleeve 58 surrounds the bellows, plate and load spring and acts as a casing therefor, having one end abutting against the casing l and the other end covered by a cap 59 which is secured thereto by screws 60. A central opening is providedin cap 59 through which a part of the knob 1 extends. Knob 51 is provided with a circular shoulder 6| slightly larger 50.. against or very nearly against the cap 59 and .a washer 62 is riveted to the knob on the other side of the cap in such a manner that the load spring 55, acting on the knob through the bellows, holds the washer constantly against; the cap. whereby longitudinal movement of the kno is prevented.

The bellows 54 is connected to a bulb 63 by. a s flexible capillary tube 84 which passes through a slot in sleeve 54. The helows, bulb and eapll- 7o, lary tube arefllied with a suitable thermally re- 4 sponsite fluid. The bulb has a greater capacity than the tube and bellows and should be placed in the medium to be controlled. Then as the temperature of the medium is raised by the heat of the main burner, the thermally responsive fluid will be expanded, which in turn will cause the bellows to be expanded. When the bellows expands, the gland pin 5| is moved to the right to actuate the main lever 23 to snap the mechanism and close the valve, shutting off the supply of fuel to the main burner. As the medium subsequently begins to cool, the bellows contracts to remove the force of the pin 5| from lever 23, whereupon the valve will be snapped open to again pass fuel to the burner to maintain the medium at a uniform temperature. 1

A collar 66 is carried on pin 5| and is held stationary by the set screw 61. This collar is arranged to abut against the wall of the chamber 2| to'limit the movement of the pin 5| to the left,

, which will also limit the lclockwise movement or the main lever 23 about its'pivot. As mentioned hereinbefore, the tension spring 21 is constantly tending to rotate the main lever 23 in clockwise direction and contraction of the bellows 54 will allow such movement to take place, providing, of course, that the pilot is burning. The purpose of the limiting means is to stop the movement of said main lever in the clockwise direction shortly after the valve has been opened as a result of such movement. The force exerted on the main lever by the tension spring is then absorbed by the limiting means. Otherwise, this force would be transmitted through the leverto the rod and tube thermostat, which, being in a heated condition, is liable to slight distortion under continual pressure. The collar 66 is searate from the pin and should be adjusted along the pin 5| to the proper position and the set screw 61 then tightened tohold the collar in place.

The provision of structure of this type because without such means the thermostat is liable to become distorted and the device consequently rendered inoperative. The limiting means does not interfere with the operation of the device but does prevent a pressure load from being placed on' the hot thermostat.

Since longitudinal movement of the knob is prevented, rotation thereof will act through the threaded connection with the bellows to change the bellows position which will vary the amount of expansion necessary to operate the snap acting mechanism. Thus the temperature at which the medium will be maintained may be adjusted by rotating the knob 51. A pointer 65-, carried by the knob 51, is arranged to cooperate with appropriate indicia inscribed on the cap 59.

Bearing against the lower end of the main lever 23 on the opposite side thereof from the pin 5|, is another smaller gland pin 68' which extends therefrom through the wall of chamber 2| to engage an auxiliary control member lever 69. The lever 69 has one end pivoted on an ear 10 which protrudes from the casing I, while the other end may be used for operating a device such as a switch or valve for regulating a suitable auxiliary device such as a fan or an air shutter as previously mentioned. A very light spring is positioned between the wall of chamber 2| and a shoulder carried by the pin 68 and serves to keep the pin 68 in constant engagement with'the main lever 23 so that the pin 68 will be moved as the main lever is moved.

The general operation of the structure hereinbefore described is as follows: The pointer 65 is set to the temperature at which it is desired to the above described movement limiting means is exceedingly important in' a.

maintain the medium in which the bulb is located. The main gas cook 5 is then turned on but since the valve 6 is not yet open, no gas will be supplied to the heating burner. Then the pilot gas cock 45 is opened, the pilot ignited and the size of the flame 43 adjusted by the valve 41. Flame 43 heats the rod and tube thermostat and the influence of the rod 38 is withdrawn from the snap acting mechanism. When this is done and if the temperature of the medium is below that desired, the valve 6 will be snapped open to supply fuel to the heating burner. When the temperature of the medium reaches that desired, the pin 5| will be moved to the right and the valve 6 closed. Thereafter, the medium will begin to cool which will result in the valve being reopened and the cycle repeated. However, if at any time the pilot flame is extinguished, the rod 38 will bear against the main lever of the snap acting mechanism to cause the valve to be closed and held in that position until the pilot is re-ignited.

Throughout the above operation the pin 68 follows the movement of the main lever of the mechanism to actuate the auxiliary control lever 69.

Thus as the valve is opened the lever 69 is moved to one position and as the valve is closed the lever 69 is moved to the opposite position.

As mentioned before, it is important that the snap acting mechanism be arranged to constantly tend; of itself, to open the valve. The thermostats then serve to actuate the mechanism to efiect the closure and to allow the opening of the valve. Such an arrangement makes it possible for either thermostat to actuate the mechanism to close the valve independently of the other and since the thermostats have a pressure bearing engagement with the mechanism, the forces developed thereby will never oppose each other.

Although I have illustrated and described a preferred form of my invention, it is not necessarily limited thereto, as it may be otherwise embodied within the scope of the appended claims.

I claim:

l. A thermostatic control device comprising a valve, a lever mechanism for operating said valve including a snap acting lever engageable therewith, a thermostat arranged to actuate said mechanism to snap said lever and eflect snap opening and closing of said valve, and a second thermostat positioned to actuate said mechanism to snap said lever and effect snap closing of said valve independently of said first thermostat.

2. In. a thermostatic control for use with a heating burner and a pilot burner, a valve for controlling the flow of fuel to said heating burner, a lever mechanism for operating said valve in' cluding a spring operated, snap acting lever engageable therewith, a thermostat responsive to temperatures caused by said heating burner and operable to actuate said mechanism and snap said lever to operate the valve in accordance with temperature variations, and a second thermostat lever mechanism including a spring operated, snap said spring tendency in accordance with temperature variations and eifect a reciprocating snap movement of said member, and a second thermostat positioned to.actuate said mechanism in opposition to said spring tendency and eifect snap movement of said member in the second direction member, said spring being arranged to constantly tend. of .ltself, to snap said lever and move said member in one direction, and a plurality of thermostats positioned to indepeiidently actuate said mechanism in opposition to said spring tendency to effect snap movement of said member in the seoonddirection, said thermostats having a pressure bearing engagement with said mechanism, whereby the forces exerted upon the mechanism by the thermostats will never oppose each other.

5. In a thermostatic control device, a control member movable in two opposite directions, a

acting lever operiitively engageable with said member, said spring being arranged to constantly tend, of itself, to snap saidlever and move said member in onc direction, a thermostat located in a first heat zone and arranged to engage said mechanism to oppose said spring tendency in accordance with temperature variations to efiect a reciprocating snap movement of said member, and a second thermostat located in a second heat zone and arranged to actuate said mechanism in opposition to said spring tendency to effect snap movement of said member in the second direction independently of said first thermostat upon the development of an abnormal temperature therein, said second therm ostat being normally disengaged fromss'aid mechanism to permit free movement control operating lever pivotally mounted in said thereof by said first thermostat.

6. In a thermostatic control for use with a heat 'ing burner-and apilot'burner, a valve for controlling tl efiow .of fuel to said heating burner, a

' lever mechanism including a spring operated, sna

ing said mechanism to oppose said spring tendency andefiect snap closing and opening of said valve in accordance with temperature variations, and a second thermostat responsive to pilot temperatures for actuating said mechanism in opposition to said'spring tendency to cause snap closing of said valve .independently of said first thermostat upon extinguishment of the flame at said pilot burner. I

I. In a control device for use with a heating burner and a pilot burner, a casing, a valve therein for controlling the flow of ,fuel to said heating burner, a secondary or valve operating lever mounted in said casing, a main lever in said easing, a spring interconnecting said levers to impart snap movement to said secondary lever to open and close said valve when the main lever is movedgradually in opposite directions, said spring being arranged to constantly tend, of itself, to move said main lever in a direction to' cause snap opening of said valve, a thermostat responsive to temperatures afiected by said heating burner for actuating said main lever in opposition to said spring tendency and control snap opening and closing of said valve in accordance with temperature variations, and a second thermostat responsive to pilot temperatures for actuating said main lever in opposition to said spring tendency to cause snap closing of said valve independently of said first thermostat upon extinguishment of the flame at said pilot burner.

8. A device as set forth in claim '1 in which the thermostats have a pressure bearing engagement with said main lever, and said second thermostat remains disengaged fromsaid main lever as long as there is a fiame at said pilot burner, whereby the forces developedby the two thermostats will never oppose each other.

, 9, -A thermostatic control device comprising control means, a lever mechanism including a lever movable in two opposite directions for operating said control means said mechanism being arranged when actuated to operate said lever with a snap action, a thermostat arranged to actuate said mechanism and snap said lever back and forth, and a second thermostat arranged to actuate said mechanism and snap said lever in one direction independently of said first thermostat.

10. A thermostatic control device comprising a casing, a control member therein, a secondary or casing,v a main lever pivotally mounted intermedinecting said levers, the levers and spring being so arranged thatgradual movement of said main lever will impart a snap movement to the secondary lever, said spring being positioned to constantly tend to move said main lever in a first direction about its pivot, and a pair of thermostats positioned to independently engage opposite ends of the main lever to move same in a second and opposite direction about its'pivot, said thermostats having pressure bearing engagements with the main lever, whereby said main lever may be moved in said second direction by either thermostat but it may be moved in the first direction only when both thermostats concur in permitting such movement." I

nonna'r E. mswmn g CERTIFICATE OF CORRECTION. Patent No. 2,163,80L ,Q f-'27, 959- ROBERT E. NEwELL;

It is hereby certified that error appears jthe pri'hted specification of the above numbered patent requiring correction as follows-z Page 1;, first 1mm; line for t read separate; same p age'a'nd column, 62, and second column, lines 2h, 25, and 27, for the reference numeral read 69' same pagel first column, lines 69, 70, and 71, and second umn, line 22, for the reference numeral "68" read 68' and that the Letters Patent should be read with this correction therein that the may conform to the record of the case in the Patent Office.

Signed and sealed this 8th day of August, A. D. 1939.

. LeslieFrazer, (Seal) line col-

said

same

Acting Commissioner of Patents. 

